1. Technical Field
The present disclosure generally relates to well bore tools and in particular to apparatus and methods for estimating downhole fluid properties.
2. Background Information
Oil and gas wells have been drilled at depths ranging from a few thousand feet to as deep as five miles. A large portion of the current drilling activity involves directional drilling that includes drilling boreholes deviated from vertical by a few degrees up to horizontal to increase the hydrocarbon production from earth subterranean formations.
Information about the subterranean formations traversed by the borehole may be obtained by any number of techniques. Some techniques used to obtain formation information include obtaining one or more core samples of the subterranean formations and obtaining one or more fluid samples produced from the subterranean formations. These samplings are collectively referred to herein as formation sampling. Modern fluid sampling includes various downhole tests and sometimes fluid samples are retrieved for surface laboratory testing.
One test that may be performed on downhole fluid includes estimating the refractive index of the downhole fluid using a light source emitting a light to a fluid interface and then measuring an intensity of light reflected or refracted at the interface. Changes in refractive index can be used to monitor fluid sample cleanup from mud-filtrate-contaminated fluid to nearly pure formation fluid. Also, fluid refractive index correlates to fluid density and polarizability.